nfc(app): Add API to return default NFC SubscriptionId

For devices that have UICC/EUICC configured to serve as NFCEE, this API
will return the subscription ID of default NFCEE.

Bug: 321314635
Test: atest CtsNfcTestCases
Change-Id: I1f80859f0d0a95a5bb4490a0fdf6afed1b9b8b2f
1 file changed